Migratory history of the freshwater goby Rhinogobius sp CB in Japan

The migratory histories of Rhinogobius sp. CB collected from 32 locations connected to the sea were studied by examining the strontium (Sr) and calcium (Ca) concentrations in the otoliths using X-ray electron microprobe (EPMA) analysis. The Sr and Ca contents in the riverine water were also determined using inductively coupled plasma mass spectrometry (ICP-MS) analysis. The Sr:Ca ratios in the riverine waters were highly different among rivers and correlated with those in the otolith outer region corresponding to the river life period. Consequently, almost all samples (159 of 160 individuals) showed a typical amphidromous life history, with one individual showing a landlocked life history. These results suggest that the clear differences of migration history in population or locality were not found in Rhinogobius sp. CB. Therefore, it was thought that Rhinogobius sp. CB most commonly had an amphidromous life history.